Polyurethanes, such as flexible and rigid foams, elastomers, sealants, and the like, are usually formulated as crosslinked polymers, so they typically cannot be reclaimed or recycled by simply melting the polymer and remolding it. Recycling of polyurethanes requires chemical conversion of the polymer. It is known, for example, to perform basic hydrolysis of polyurethanes at elevated temperatures to isolate components derived from the polyol, polyisocyanate, and chain extender reactants. Recovery and reuse of these components is complicated by the presence of catalysts, surfactants, fillers, flame retardants, and other additives commonly used to manufacture polyurethanes. The high cost of purification makes this strategy impractical and commercially unattractive.
A more attractive approach avoids purification of the individual components following chemical conversion of the polyurethane. In this strategy, the polyurethane is converted to a liquid form or is dissolved in a liquid polymer. The liquid product is then used to manufacture another polyurethane. U.S. Pat. Nos. 2,937,151, 3,109,824, and 3,117,940, and German Patent DE 3,435,014 illustrate this approach.
In copending application Ser. No. 07/979,760, filed Nov. 23, 1992, we described a new ester insertion process in which a cyclic, unsaturated anhydride inserts randomly into carbon-oxygen bonds of a polyether to give an unsaturated polyetherester resin. Unlike conventional unsaturated polyester resins, the degree of unsaturation in the product can be easily controlled by adjusting the ratio of polyether to cyclic, unsaturated anhydride. Thus, unsaturated polyetherester resins having a wide range of crosslinkabilities can be made from maleic anhydride and a single polyether polyol.
Particularly needed in the art are ways to convert scrap polyurethane foams, elastomers, and the like, directly to useful liquid polymer resins without the need to first isolate polyether polyols from the other components. Ways to convert scrap polyurethanes to polymers other than polyurethanes, such as thermoset plastics, are also needed.